Influenza vaccine uptake among health care professionals (HCPs) has remained stubbornly low, despite its importance for patient safety and public health preparedness. To increase coverage rates, a small number of states, including California, have implemented default influenza vaccination mandates that require HCPs to be vaccinated unless they actively "opt-out" by signing a formal declination. Mandates with strict penalties for non- participation may be a particularly effective means of achieving high vaccination rates. Our preliminary data suggests that nationally, uptake of seasonal vaccine is roughly twice as high among HCP subject to employer mandates compared to those who are not. While still rare, such programs are highly controversial and, have generated high-profile litigation in California and elsewhere. Such controversy may render implementation of strict mandates practically infeasible. Implementation requires careful consideration of various design options, including accompanying educational interventions and conditions for opting out to ensure that programs are effective and accepted by employees. However, there is little evidence regarding the effectiveness and acceptability of mandatory vaccination programs. To fill this gap in knowledge, the proposed study will evaluate the impact of a 2006 law requiring that hospital employees in California be vaccinated for influenza using data from two sources : (1) survey data comparing self-reported change over time in influenza vaccine uptake and factors relating to the acceptance of vaccine mandates for hospital employees in California and their counterparts employed in other states and (2) qualitative interviews conducted with administrators of acute- care hospitals, public health authorities, and professional organizations in California to assess barriers to and facilitators of the implementation of the mandate and the impact of the law on planning and response to the 2009 A(H1N1) pandemic. The proposed project will generate rigorous data on California's experiences implementing mandatory influenza vaccination. The efficiency of our effort and the comparability of our results will be enhanced by our ongoing efforts to collect nationally representative data on uptake of influenza vaccine and vaccine-related knowledge and attitudes among HCP and the general population of adults in the US. Because California is a large state with wide diversity among its hospitals and hospital employees, the results of our evaluation will provide a strong empirical basis to inform strategies for increasing the acceptance of mandatory vaccination by employees of California Hospitals and strategies being considered by other states for reducing the serious and preventable threat to patient safety and public health posed by outbreaks of seasonal and pandemic influenza. PUBLIC HEALTH RELEVANCE: California requires hospital employees to be vaccinated against influenza unless they actively "opt-out" by signing a formal declination. The proposed study will evaluate the impact of this mandate using qualitative and quantitative data sources from two sources. The results of our evaluation will provide a strong empirical basis to inform strategies for increasing the acceptance of mandatory vaccination by employees of California hospitals and strategies being considered by other states for reducing the serious and preventable threat to patient safety and public health posed by outbreaks of seasonal and pandemic influenza.